We developed a synthesis system for production of ^<11>C-FLB457 and ^<11>C-raclopride, and measured the cortical dopamine D_2 receptor binding in normal volunteers and patients with Parkinsonian symptoms. The subjects consisted 9 normal volunteers and 18 patients, including 7 patients with Parkinson's disease, 5 patients with striato-nigral degeneration, 3 patient with progressive supranuclear palsy, 2 patients with corticobasal degeneration and a patient with diffuse Lewy body disease. 7.9-22.4 mCi of ^<11>C-FLB457 or ^<11>C-raclopride was intravenously administered as a bolus. The data were collected for every 1 min (0-4 min), every 2 min (4-20 min), every 5 min (20-60 min) and every 15 min (63-78, 80-95 min). The cortical D_2 receptor binding was evaluated by the graphical analysis using Logan's plot and the transient equilibrium method with individually determined plateau time. We used the cerebellum as a reference region of non-specific binding site. The cortical D_2 receptor binding measured by these methods were well correlated with each other. In normal volunteers, the cortical D_2 receptor binding gradually decreased with age, but apparent decline was not observed. The cortical D_2 receptor binding decreased in the frontal region of a patient with diffuse Lewy body disease, while it was preserved in Parkinson's disease, striato-nigral degeneration and corticobasal degeneration.